The term cancer collectively refers to more than 100 different diseases that affect nearly every part of the body. Throughout life, healthy cells in the body divide, grow, and replace themselves in a controlled fashion. Cancer starts when the genes directing this cellular division malfunction, and cells begin to multiply and grow out of control. A mass or clump of these abnormal cells is called a tumor. Not all tumors are cancerous. Benign tumors, such as moles, stop growing and do not spread to other parts of the body. But cancerous, or malignant, tumors continue to grow, crowding out healthy cells, interfering with body functions, and drawing nutrients away from body tissues. Malignant tumors can spread to other parts of the body through a process called metastasis. Cells from the original tumor break off, travel through the blood or lymphatic vessels or within the chest, abdomen or pelvis, depending on the tumor, and eventually form new tumors elsewhere in the body.
Only 5–10% of cancers are thought to be hereditary. The rest of the time, the genetic mutation that leads to the disease is brought on by other factors. The most common cancers are linked to smoking, sun exposure, and diet. These factors, combined with age, family history, and overall health, contribute to an individual's cancer risk.
Several diagnostic tests are used to rule out or confirm cancer. For many cancers, a biopsy is the primary diagnostic tool. However, many biopsies are invasive, unpleasant procedures with their own associated risks, such as pain, bleeding, infection, and tissue or organ damage. In addition, if a biopsy does not result in an accurate or large enough sample, a false negative or misdiagnosis can result, often requiring that the biopsy be repeated. What is needed in the art are improved methods to specifically detect, characterize, and monitor specific types of cancer.